fix: c and c++ to match styleguide

[jack-mil]

I think all languages with "C-style" syntax use basically the same groups. I have yet to figue out what "PREPROCESSOR COMMENT" and "PREPROCESSOR COMMENT DOC" actuall do for these languages.

They all (C, C++, Java, C#) provide seperate highlight groups for Instructions words (if/while/return,etc) and Type words (int/double/template/class/public, etc). For now, I have made everything mauve, because these are all 'keywords'. However, it does make everything a similar color, and there is no blue in use (usually reserved for functions). We might experiment with using blue for one of these groups across the board, if it looks better (see below).

C	C++

Example with `blue` Type Words (not in this commit)

Relates to #17

[InvitedToHell]

mhmm. What is it like in the VSCode/Vim theme rn?

[jack-mil]

I messed up fixing conflicts because I forgot this branch was still on my fork and not this repo. This PR is ready to go now.